The present invention relates to a trimming circuit, and more particularly to a fuse trimming circuit for adjusting electric characteristics of a semiconductor integrated circuit.
Conventionally, electric characteristics of a semiconductor integrated circuit are adjusted by breaking a fuse of a trimming circuit before shipment of the circuit. The accuracy of the semiconductor integrated circuit is enhanced by the adjustment. The fuse is broken by applying a current or a voltage to the fuse or by irradiating the fuse with a laser. However, the breakage of the fuse by laser beam irradiation requires a relatively large laser beam generation apparatus, and therefore is not feasible for a manufacturing environment.
In the prior art, it has been difficult to predict exactly what the electric characteristics of the semiconductor integrated circuit will be after the fuse is broken. Therefore, in some cases, a fuse is broken that should not be, and a defective semiconductor integrated circuit is shipped. Therefore, before the fuse is broken, a careful determination of the procedures for testing the characteristics of the circuit and breaking the fuse is required.
To confirm the electric characteristics of the semiconductor integrated circuit before the fuse is broken, a trimming circuit is used to perform hypothetical fuse breakage. The trimming circuit includes a transistor connected in series to a fuse formed of polysilicon (polyfuse). The fuse is brought to a hypothetical broken state by controlling an activated/inactivated state of the transistor. Thereby, the electric characteristics of the semiconductor integrated circuit after the breakage of the fuse are accurately predicted before the breakage, and the fuse to be broken is securely selected.
The trimming circuit includes N polyfuses and N transistors, each connected to one polyfuse, for controlling each hypothetical polyfuse breakage. The trimming circuit further includes a control terminal for receiving a transistor control signal, and Nxc3x97N trimming terminals. The trimming terminals and control terminal are electrodes (pads) formed on a substrate for connecting the semiconductor integrated circuit to an external lead wire or a bump. The transistors are relatively large sized to bear a high voltage or a large current for breaking the polyfuses. Therefore, the semiconductor integrated circuit including the trimming circuit is relatively large-sized.
Moreover, in order to finely adjust the electric characteristics of the semiconductor integrated circuit, the number of polyfuses is preferably large. However, the number of trimming terminals increases in accordance with the number of polyfuses. Therefore, the trimming terminals, which are used only during trimming, enlarge the semiconductor integrated circuit.
It is an object of the present invention to provide a relatively compact trimming circuit for hypothetically breaking a fuse.
To achieve the above object, the first aspect of the present invention provides a trimming circuit including a resistor connected to either one of a first power supply and a second power supply and at least one trimming element connected between the other one of the first power supply and the second power supply and the resistor. The trimming circuit further includes at least one resistance bypass circuit, connected to a node between the resistor and the at least one trimming element, for selectively performing ordinary breakage and hypothetical breakage of the trimming element in accordance with a control signal and a data signal. The at least one resistance bypass circuit holds the at least one trimming element in an unbroken state in accordance with the control signal during the hypothetical breakage. The at least one resistance bypass circuit connects the at least one trimming element to the first power supply and the second power supply in accordance with the control signal and the data signal and breaks the trimming element during the ordinary breakage. An output changeover circuit, which is connected to the node, generates a first output signal in accordance with a state of the at least one trimming element during the ordinary breakage and generates a second output signal in accordance with the data signal during the hypothetical breakage.
The second aspect of the present invention provides a trimming circuit including a resistor connected to either one of a first power supply and a second power supply and at least one trimming element connected between the other one of the first power supply and the second power supply and the resistor. The trimming circuit further includes at least one resistance bypass circuit, connected to the at least one trimming element, for supplying the first power supply and the second power supply to the trimming element in accordance with a control signal and a data signal to selectively perform ordinary short-circuit and hypothetical short-circuit of the trimming element. The resistance bypass circuit holds the trimming element in a non-short-circuit state in accordance with the control signal during the hypothetical short-circuit and connects the trimming element to the first power supply and the second power supply in accordance with the control signal and the data signal to short-circuit the trimming element during the ordinary short-circuit. An output changeover circuit, which is connected to the node, generates a first output signal in accordance with a state of the at least one trimming element during the ordinary short-circuit and generates a second output signal in accordance with the data signal during the hypothetical short-circuit.
The third aspect of the present invention provides an adjustment circuit for controlling a plurality of adjustment elements. The adjustment circuit includes a plurality of switch elements connected in parallel with the plurality of adjustment elements, and a plurality of trimming circuits, connected to the plurality of switch elements, for receiving a plurality of data signals and a common control signal. The trimming circuit has a resistor connected to either one of a first power supply and a second power supply, at least one trimming element connected between the other one of the first power supply and the second power supply and the resistor, at least one resistance bypass circuit, connected to a node between the resistor and the at least one trimming element, for selectively performing ordinary breakage and hypothetical breakage of the trimming element in accordance with the control signal and the data signal. The at least one resistance bypass circuit holds the at least one trimming element in an unbroken state in accordance with the control signal during the hypothetical breakage and connects the at least one trimming element to the first power supply and the second power supply in accordance with the control signal and the data signal to break the trimming element during the ordinary breakage. An output changeover circuit is connected to the node to generate a first output signal in accordance with a state of the at least one trimming element during the ordinary breakage, and to generate a second output signal in accordance with the data signal during the hypothetical breakage.
The fourth aspect of the present invention provides a semiconductor apparatus including a plurality of data terminals for receiving a plurality of data signals, a control terminal for receiving a common control signal, a plurality of adjustment elements, a plurality of switch elements connected in parallel with the plurality of adjustment elements, and an adjustment circuit, connected to the plurality of switch elements, the plurality of data terminals and the control terminal, for switching the plurality of switch elements in accordance with the plurality of data signals and the common control signal to control the adjustment element. The adjustment circuit has a plurality of trimming circuits connected to the plurality of switch elements. The trimming circuit includes a resistor connected to either one of a first power supply and a second power supply, at least one trimming element connected between the other one of the first power supply and the second power supply and the resistor, and at least one resistance bypass circuit, connected to a node between the resistor and the at least one trimming element, for selectively performing ordinary breakage and hypothetical breakage of the trimming element in accordance with the control signal and the data signal. The at least one resistance bypass circuit holds the at least one trimming element in an unbroken state in accordance with the control signal during the hypothetical breakage and connects the at least one trimming element to the first power supply and the second power supply in accordance with the control signal and the data signal and breaks the trimming element during the ordinary breakage. The trimming circuit also includes an output changeover circuit for generating a first output signal in accordance with a state of the at least one trimming element during the ordinary breakage, and generating a second output signal in accordance with the data signal during the hypothetical breakage.
The fifth aspect of the present invention provides a semiconductor apparatus including a plurality of data terminals for receiving a plurality of data signals, a control terminal for receiving a common control signal, a plurality of adjustment elements, a plurality of switch elements connected in parallel with the plurality of adjustment elements, and an adjustment circuit, connected to the plurality of switch elements, the plurality of data terminals and the control terminal, for switching the plurality of switch elements in accordance with the plurality of data signals and the common control signal to control the adjustment element. The adjustment circuit has a plurality of trimming circuits connected to the plurality of switch elements. The trimming circuit includes a resistor connected to either one of a first power supply and a second power supply, at least one trimming element connected between the other one of the first power supply and the second power supply and the resistor, and at least one resistance bypass circuit, connected to the at least one trimming element, for supplying the first power supply and the second power supply to the trimming element in accordance with the control signal and the data signal to selectively perform ordinary short-circuit and hypothetical short-circuit of the trimming element. The resistance bypass circuit holds the trimming element in a non-short-circuit state in accordance with the control signal during the hypothetical short-circuit and connects the trimming element to the first power supply and the second power supply in accordance with the control signal and the data signal to short-circuit the trimming element during the ordinary short-circuit. The trimming circuit also contains an output changeover circuit, connected to the node, for generating a first output signal in accordance with a state of the at least one trimming element during the ordinary short-circuit, and generating a second output signal in accordance with the data signal during the hypothetical short-circuit.